A liquid crystal modulation element provides a delay for a light wave which passes a liquid crystal layer using an electronically controlled birefringence effect to change a polarization condition of the light wave, thereby forming image light. For example, a liquid crystal modulation element serving as a two-dimensional pixel light switch is used as a liquid crystal projector of an image modulation element of a projection display device.
Since the liquid crystal modulation element, i.e. a liquid crystal lens, depends on a polarization state of incident light and natural light needs to be modulated by a liquid crystal lens composed of a double-layer liquid crystal cell, a thickness of a whole device thereof increases accordingly in the related art.